watchdog: designware: Migrate CONFIG_DESIGNWARE_WATCHDOG to Kconfig

Migrate CONFIG_DESIGNWARE_WATCHDOG to Kconfig and update the headers
accordingly, no functional change. The S10 enables the WDT only in
SPL, but does not enable it in U-Boot itself, hence disable it in
the config again.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Chin Liang See <chin.liang.see@intel.com>
Cc: Dalon Westergreen <dwesterg@gmail.com>
Cc: Dinh Nguyen <dinguyen@kernel.org>
Cc: Jagan Teki <jagan@amarulasolutions.com>
Cc: Ley Foon Tan <ley.foon.tan@intel.com>
Cc: Philipp Tomisch <philipp.tomisch@theobroma-systems.com>
Cc: Simon Goldschmidt <simon.k.r.goldschmidt@gmail.com>
Cc: Tien Fong Chee <tien.fong.chee@intel.com>
diff --git a/configs/socfpga_stratix10_defconfig b/configs/socfpga_stratix10_defconfig
index c7286d5..a83d991 100644
--- a/configs/socfpga_stratix10_defconfig
+++ b/configs/socfpga_stratix10_defconfig
@@ -59,3 +59,4 @@
 CONFIG_USB_DWC2=y
 CONFIG_USB_STORAGE=y
 # CONFIG_SPL_USE_TINY_PRINTF is not set
+CONFIG_DESIGNWARE_WATCHDOG=y